1. Field of the Invention
The invention relates to water softener control valves and, more particularly, relates to a water softener control valve with a readily removable seal stack and to its methods of assembly and disassembly. The invention additionally relates to a water treatment system employing such a control valve and to methods of installing and removing a seal stack from such a control valve.
2. Discussion of the Related Art
Water softeners are widely used for removing calcium and other deposit causing materials from so-called xe2x80x9chard water.xe2x80x9d The typical water softener relies on an ion exchange process taking place in an ion-exchange resin bed stored in a resin tank of the water softener. As the water to be processed passes through the resin-filled tank, ions of calcium and other minerals in the water are exchanged with ions found in the resin, e.g., sodium, thereby removing objectionable ions from the water and exchanging them for less objectionable ions from the resin.
The capacity of the resin to exchange ions is finite and is reduced during the ion exchange process. If measures are not taken to regenerate the resin by replacing the undesirable ions with desirable ions, the ion exchange capacity of the resin will become exhausted. Water softeners are typically configured to periodically regenerate the ion exchange resin stored in the resin tank. Regeneration typically involves chemically replacing the objectionable ions such as calcium ions from the resin with less objectionable ions such as sodium ions. This replacement is typically performed by introducing a regenerant solution of sodium chloride or potassium chloride into the resin bed from a brine tank and thereafter flushing the regenerant solution from the bed. Regeneration of a water softener resin bed is sometimes accomplished in a direction that is co-current with the flow of water to be treated (often referred to as xe2x80x9cdownflow regenerationxe2x80x9d) and is sometimes accomplished in a direction that is countercurrent to the flow of water being treated (often referred to as xe2x80x9cupflow regenerationxe2x80x9d). The resin bed is typically backwashed in order to remove trapped particulate matter, and the resin tank can be rinsed to remove objectionable soluble materials. In order to prevent interruption of service, most water softeners are configured to allow bypass flow of untreated water directly to the service lines during backwash, rinse, and regeneration. All of these operations are known in the art.
The regeneration cycle is typically controlled by a control valve mounted on top of the resin tank. The control valve is coupled to a source of untreated water, a treated water or service outlet line, the brine tank, a drain connection, and the resin tank. The typical control valve is controlled by an electric motor under the control of a timer and/or a usage indicator to cycle the water softener from service, brine introduction, backwash, fast rinse, and back to service.
Several different types of control valves have been used in water softeners. Some are of the rotary disc type, in which the motor rotates a three-dimensional valve member to selectively connect and cover various inlet and outlet ports in the valve body bore in which the disc is mounted. A control valve of this type is manufactured by Eco Water of Woodbury, Minn. Another control valve type, manufactured by Osmonics, comprises modified poppet valves. These multiple valve elements are independently actuated by cams. Still others are of the so-called reciprocating piston type, in which the motor drives a piston to reciprocate axially in a bore to selectively connect and cover various inlet and outlet ports in the bore. See, for example, U.S. Pat. No. 3,700,007 to Sparling and U.S. Pat. No. 4,290,451 to Fleckenstein et al. The invention relates to water softeners employing reciprocating piston-type water softener control valves.
The typical reciprocating piston-type water softener control valve includes a seal arrangement that is positioned in a cylindrical bore and that surrounds the reciprocating piston. Some seal stack arrangements are formed from several spacers, static seals, and dynamic seals which are stacked in the cylindrical bore. The static and dynamic seals can be separate members or combined to form a single unitary member. Assembly and disassembly of these seal stacks can be difficult tasks requiring considerable skilled labor. For instance, in one such arrangement, manufactured by Fleck Controls and described to an extent in the Fleckenstein et al. patent, all components of the seal stack are loose and independent of one another. This seal stack must be assembled in the bore by first inserting a spacer into the bore, then inserting a seal, then inserting another spacer, etc. This assembly process is tedious. It can often be difficult to implement because the seals tend to get trapped between the edges of spacers and the bore and then get pinched or cut as the seal stack assembly is tightened down. The resultant damage to the valve could degrade or ruin its operation, but might not be visually apparent. As such, any damage to the valve might not be evident until it fails in the field.
In another type of arrangement known to the inventors, Culligan and Fleck both designed a preassembled seal stack in which the spacers and seals of the stack are screwed together rigidly as a unit before the stack is inserted into the bore. In this type of arrangement, the inner and outer seals of the stack are completely compressed axially prior to insertion of the seal stack into the bore. This axial precompression results in commensurate outward radial expansion of the seals to their final diameter. The precompressed seals must be squeezed past the ports in the bore during valve assembly. This arrangement forces the designer to walk a fine line. If the seals are precompressed too much during seal stack assembly, the stack cannot be inserted into the bore without damaging the seals. If the seals are not precompressed enough during seal stack assembly, they may not provide an adequate seal against the peripheral surface of the cylindrical bore. This design therefore requires the maintenance of tight tolerances on the diameter of the bore and on the diameter of the precompressed static seals. This tolerance requirement produces substantial reliability problems.
The need therefore has arisen to provide a seal stack for a linearly reciprocating piston-type water softener flow control valve or other valve in which the seal stack can be preassembled prior to insertion into the associated bore but in which the seals of the stack need not be precompressed prior to insertion of the seal stack into the bore.
In accordance with a first aspect of the invention, the above-identified need is satisfied by providing a water softener control valve comprising a valve body which houses a valve element in the internal bore thereof. The valve element includes a piston located in the bore and a seal stack that surrounds the piston. The piston is axially slidable in the bore under the action of a controller to connect various ones of the internal ports to one another in combinations that vary depending upon the position of the piston in the bore. The seal stack includes a plurality of elastomeric static seals which seal against a peripheral surface of the bore and a plurality of dynamic seals which are disposed radially inwardly of the static seals and which seal against the piston. The seal stack is dimensioned and configured such that (1) the seal stack is compressible axially upon valve assembly to expand the static seals radially to enhance sealing contact between the static seals and the peripheral surface of the bore, and (2) upon initial removal of the seal stack axially from the bore, the seal stack expands axially to permit the static seals to constrict radially. The radial constriction diminishes sealing contact between the static seals and the peripheral surface of the bore and releases the static seals from the peripheral surface of the bore and facilitating further removal of the seal stack from the bore.
Axial compressibility of the seal stack is obtained by connecting at least some of the spacers of the seal stack to one another by lost motion connectors that permit limited axial movement therebetween. Each of the lost motion connectors preferably comprises a hook extending axially from one of the spacers and a receptacle on the adjacent spacer. The lost motion is obtained by dimensioning each of the hooks to have a leg that is substantially longer than a depth of the receptacle.
A seal stack of this or similar construction can be removed from the valve body with relatively little resistance from the static seals. The removal process begins with moving an outermost spacer of the seal stack axially outwardly relative to a first intermediate spacer, thereby permitting a first elastomeric static seal between the outermost and first intermediate spacers to constrict radially to diminish sealing contact between the static seal and the peripheral surface of the bore and to release the first static seal from the peripheral surface of the bore to facilitate further removal of the seal stack from the bore. The outermost spacer and the first intermediate spacer are then moved axially outwardly as a unit relative to a second intermediate spacer, thereby permitting a second elastomeric static seal between the first and second intermediate spacers to constrict radially to diminish sealing contact between the second static seal and the peripheral surface of the bore and to release the second static seal from the peripheral surface of the bore to facilitate further removal of the seal stack from the bore. This process is repeated until all spacers have released from the bore. The seal stack is much easier to remove from the bore than it otherwise would be, because the spacers are broken loose from the bore sequentially rather than all at once.
The sequential release of the spacers from the bore may be enabled by the use of lost motion connectors in the seal stack, in which case each of the moving steps include taking up the lost motion afforded by the associated lost motion connector.
A seal stack constructed in accordance with the invention can also be assembled and inserted into the bore of the valve body with relatively little resistance from the static seals and with little or no risk of damaging the static seals. The process begins with assembling the seal stack outside of the valve body by attaching a plurality of axially-aligned spacers to one another with static seals clamped therebetween so that an outer diameter of at least some of the static seals is less than a diameter of the bore. The preassembled seal stack is then inserted into the bore, and the seal stack is axially compressed to expand radially to enhance sealing contact between the static seals and a peripheral surface of the bore. The compressing step preferably comprises taking up the lost motion afforded by lost motion connectors connecting spacers of the seal stack.
These and other objects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation.